In iron, coal and cement industrial fields, a conveyor belt has been popularly used as a means of transporting goods. Such a conveyor belt is required to have, depending on its usage, oil resistance, heat resistance, chemical resistance, and nontoxicity and, further, high durability to withstand friction with goods being transported and their weight. In order to provide the durability to the conveyor belt, the conveyor belt is manufactured generally by using a reinforcing member such as a metal member such as a steel cord and the like or canvas made of aramid fiber and the like as a core material, to which a cover rubber is bonded in such a manner as to cover the reinforcing member, and then by volcanizing the core material together with the cover rubber. The cover rubber is used for the purpose of protecting the core material of the belt, and a life of the cover rubber may be considered as a life of the conveyor belt. In recent years, a size of the conveyor belt has been increasing, and a demand for improved durability of the cover rubber of the conveyor belt has been increasing more and more in those industrial fields.
In order to meet such a demand, there has been suggested a rubber composition for the cover rubber of the conveyor belt containing predetermined particulate carbon black and having good breaking strength, elongation, and abrasion resistance (JP-A-2000-198518). Also, there has been suggested rubber for a conveyor belt cover that contains carbon black and resin and achieves both the abrasion resistance and the cut resistance (impact resistance) (JP-A-2006-199892). However, obtaining the rubber composition that imparts good properties of all of the tensile strength, the tear resistance, the abrasion resistance, and the cut resistance to the conveyor belt has been difficult for the reason that those properties conflict with each other.
As such, the applicant has suggested a rubber composition for the conveyor belt containing, with respect to a rubber composition containing 75 to 85 mass % of natural rubber and 15 to 25 mass % of butadiene rubber, a predetermined amount of a resin composition and a vulcanizing agent (JP-A-2009-215339). However, a rubber composition for a conveyor belt that achieves balancing the tensile strength, the tear resistance, the abrasion resistance, and the cut resistance of the conveyor belt at a higher level has been desired.